KR101850910B1 - Frequency variable type bandpass-to-bandstop conversion filter using switch bank - Google Patents

Abstract

The present invention is to provide a frequency variable band pass-to-band stop conversion filter for reducing costs and a chip area, which comprises: a common inductor and capacitor for providing coupling between resonators in a band pass-to-band stop (BP-BS) mode by being switched to any one of a BP mode and a BS mode; two switch couplers positioned at both sides of the common inductor and capacitor to provide input/output coupling; and a resonator of a BP-BS mode for providing a resonance frequency of a BP mode or a BS mode.

Description

[0001] The present invention relates to a frequency variable bandpass-to-bandstop conversion filter using a switch bank,

The present invention relates to a frequency variable BP (band-pass) -to-BS (band-stop) switching filter capable of switching two existing structures of BPF (Band-Pass Filter) and BSF , Switch bank on / off characteristics, common inductors and capacitors, and switchable coupling.

Conventional methods of implementing filters and circuits that selectively perform various functions over time are to design individual filters and circuits and then connect individual filters or circuits using switches.

That is, a filter or a circuit having a desired function is selected by using a switch connected to the input / output stage. For example, an existing paper (S. Mazumder, D. Upton, and S. Kunasani, "Element-level reconfigurable direct-sample receive module for digital radar," IEEE Int. Symposium on Phased Array Systems and Technology, pp. 456-459, 2013), if a microwave filter for passing an S-band and a microwave filter for passing an X-band are connected in parallel using switches at input and output ends, band signal or pass the signal of the X-band.

However, many studies have been made on various design methods for tunable BPFs with high insertion loss and low attenuation rejection at high selectivity and stop band. The proposed structure proposed a BP-to-BS conversion filter using a ring resonator and an RF switch in a PCB (Printed Circuit Board) by controlling the coupler linkage at the source-load stage . Another way is to implement a filter that can switch to BP-to-BS mode by changing the coupling path by on / off mode switching of RF switches between source and load.

However, the proposed structures have a disadvantage in that the circuit size is large especially in the low band.

Patent Registration No. 10-1525518 (registered date 2015.05.28) Patent Registration No. 10-0614110 (registered date 2006.08.11)

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a variable bandpass-bandstop filter bank used in a broadband communication system such as a cognitive radio system, Frequency band-pass-band-stop filter for reducing the frequency of the input signal.

Other objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

According to another aspect of the present invention, there is provided a frequency-variable bandpass-bandstop switching filter using a switch bank. The bandpass-band switching filter switches between a BP mode and a BS mode, a common inductor and capacitor providing a resonator-to-resonator coupling M _1,2 (J ₁₂ ) in a band stop mode; and an input / output coupling Q _e (J ₀₁ ) located on both sides of the common inductor and capacitor Two switch couplers, a common inductor, a capacitor and any one of the switch couplers, a common inductor and a capacitor, and a switch coupler, respectively, And a resonator of a BP-BS (band pass-to-band stop) mode for providing a resonance frequency of a BS mode, wherein the resonator of the band pass- A second switch bank connected in parallel with the first switch bank, a capacitor (C1) connected in series with the first switch bank, a second switch bank connected in parallel with the first switch bank, And an inductor L1 connected in series with the bank.

Preferably, the resonance frequency is changed by adjusting the number of on and off states of a switch formed in the resonator of the BP-BS (band pass-to-band stop) mode.

Preferably, the common inductor and the capacitor include a first passive terminal having an electrical coupling value (C ₁₂ ) operating in a band pass mode to pass a specific frequency band in an input signal, and a second passive terminal a first switch for band-stop mode, the magnetic and the second passive terminal having a coupling value (L _12), switching to a signal at the input terminal of one of the first passive terminal or the second manual terminal acting as to, And a second switch for switching the output of either the first passive terminal or the second passive terminal to be outputted.

Preferably, the switch coupler includes a third passive terminal having an electrical coupling value (C ₀₁ ) operating in a band pass mode to pass a specific frequency band in an input signal, and a second passive terminal coupled in parallel with the third passive terminal And a third switch for switching the signal to be bypassed.

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Preferably, the resonator of the BP-BS (band pass-to-band stop) mode has a parasitic resistance at the switch turned on when one of a plurality of switches included in the first switch bank and the second switch bank is turned on .

Preferably, the number of off (or on) states of a plurality of switches included in the first switch bank and the second switch bank is adjusted to vary the resonance frequency.

Preferably, the resonance frequency decreases as the number of switches turned off in the BP mode increases, and the resonance frequency gradually decreases as the number of switches turned off in the BS mode increases.

Preferably, when the first switch bank and the second switch bank are both on, the mode is switched to the BP mode. When the first switch bank and the second switch bank are both off, the mode is switched to the BS mode.

Preferably, when an interference signal other than a signal to be received has an interference that is stronger than a predetermined threshold value, the BS mode is switched to the BS mode. If the interference signal is weaker than a preset threshold value, .

The frequency variable bandpass-bandstop switching filter using the switch bank according to the present invention as described above has the following effects.

First, the two variable BP / BS resonators can be operated in the BP-to-PS 2 state with the resonant frequency changing as a result of using the on / off characteristics of the switch banks and the switchable coupling structure It is possible to design a filter having a miniaturized structure.

Second, unlike the conventional method, since the two BP / BS filters use the coupling circuits as the SPDT switches, the problem of complexity in implementing the conversion filter does not occur.

Third, by implementing a filter using a common inductor, a capacitor, and a switch bank, it can be implemented in a small size in a low frequency band.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a bandpass-bandstop switching filter structure of a frequency variable bandpass filter using a switch bank according to an embodiment of the present invention; FIG.
FIG. 2 is a diagram showing in detail the structure of common inductors and capacitors between resonators in FIG.
FIG. 3 is a schematic view showing the structure of the switch coupler in FIG. 1
FIG. 4 is a diagram showing a detailed structure of the resonator in FIG.
Fig. 5 is a circuit diagram showing the characteristics of the switch bank switch of the resonator in the on / off state in Fig. 4
Fig. 6 is a circuit diagram of the BP mode and the BS mode of the resonator in Fig.
Fig. 7 is a graph showing the resonance frequency change in the BP mode and the BS mode of the resonator in Fig. 4

Other objects, features and advantages of the present invention will become apparent from the detailed description of the embodiments with reference to the accompanying drawings.

A preferred embodiment of a frequency variable bandpass-bandstop switching filter using a switch bank according to the present invention will now be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. It is provided to let you know. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and are not intended to represent all of the technical ideas of the present invention. Therefore, various equivalents It should be understood that water and variations may be present.

FIG. 1 is a configuration diagram illustrating a frequency variable bandpass-bandstop switching filter structure using a switch bank according to an embodiment of the present invention. Referring to FIG.

A common inductor and capacitor 100 that switches to either the BP mode or the BS mode to provide coupling M _1,2 (J ₁₂ ) between the resonators, as shown in FIG. 1; Two switch couplers 200 located on both sides of the capacitor 100 to provide input / output couplings Q _e (J ₀₁ ), and two switch couplers 200 positioned between the common inductor and the capacitor 100 and the switch coupler 200, And a resonator 300 of a band pass-to-band stop (BP-BS) mode that provides a resonance frequency of the BP-to-BS mode using characteristics in a switch on / off state. At this time, the resonance frequency is changed by adjusting the number of on and off states of the switch in the resonator 300.

On the other hand, when designing the filter, when the resonance frequency of the resonator 300 is determined, a design index of FBW (fractional band width) should be determined. FBW is the ratio of bandwidth corresponding to 3-dB insertion loss versus center frequency. Therefore, to design a filter with the desired FBW, it is necessary to set Q _e (J ₀₁ ) and M _1,2 (J ₁₂ ) to affect the FBW. The switchable coupling of the present invention is a coupling between the input / output stage and the resonator 300, which comprises an L, C module element (lumped element) and an SPDT switch. This makes it possible to independently select an appropriate coupling circuit in each mode of BP / BS.

As shown in FIG. 2, the common inductor and the capacitor 100 include a first passive terminal having an electrical coupling value C ₁₂ operating in a band pass mode to pass a specific frequency band in an input signal A second passive terminal 120 having a magnetic coupling value L ₁₂ operating in a band-stop mode to block a specific frequency band from an input signal; 110 or the second passive terminal 120 and a switch 130 for switching the output of either the first passive terminal 110 or the second passive terminal 120 to be output, And a second switch 140 connected to the second switch 140. [

The switch coupler 200 is located on both sides of the common inductor and the capacitor 100 and is connected to an electrical coupler 200 operating in a bandpass mode to pass a specific frequency band in the input signal, A third passive terminal 210 having a ring value C ₀₁ and a third switch 220 connected in parallel with the third passive terminal 210 to switch a signal inputted thereto to be bypassed .

The resonator 300 includes a first switch bank 310 and a second switch bank 310. The first switch bank 310 is connected between the common inductor and the capacitor 100 and the switch bank 200 and has a plurality of switches connected in parallel as shown in FIG. A second switch bank 320 connected in parallel with the first switch bank 310 and connected in parallel to the first switch bank 310, a capacitor C1 connected in series with the first switch bank 310, And an inductor L1 connected to the switch bank 320 in series.

5 (a), when one of a plurality of switches included in the first switch bank 310 and the second switch bank 320 is turned on, the resonator 300 is turned on, Likewise, a parasitic resistance (a very small value of resistance) is generated at the switched on. 5 (c) shows a case where a plurality of switches included in the first switch bank 310 and the second switch bank 320 are all off. In this case, parasitic resistance by the switch is not generated do. At this time, the first and second switch banks 310 and 320 are formed of a single pole double throw (SPDT) switch.

6 (a) is a signal-processed circuit diagram showing a BP mode through a common inductor and a switch bank of the capacitor 100 and the resonator 300, and FIG. 6 (b) And a BS mode through a switch bank of the resonator 300. In the circuit diagram of FIG. That is, when the first switch bank 310 and the second switch bank 320 are both on (at least one of the switches is on), the mode is switched to the BP mode. When all of the switches are off, the mode is switched to the BS mode.

When the number of the OFF states of the switch banks is adjusted, the resonance frequency of the resonator 300 can be varied because the equivalent capacitance changes. For example, as shown in FIG. 6 (a), in the BP mode, since the equivalent capacitance becomes larger as the value of a2 * Coff becomes larger (as the number of switches that are turned off is larger), the resonance frequency shown in FIG. . In addition, as shown in Fig. 6A, since the equivalent capacitance becomes larger as the value of a1 * Coff becomes larger (the number of switches turned off becomes larger) in the BS mode, the resonance frequency shown in Fig. 7B becomes smaller .

If the number of off (or on) states of a plurality of switches included in the first switch bank 310 and the second switch bank 320 is adjusted, the equivalent capacitance is changed, 300 can be changed as shown in Figs. 7 (a) and 7 (b).

With this structure, it is possible to design a filter of a miniaturized structure that can operate in the BP-to-PS 2 state (BP mode) (BS mode) with the resonance frequency changing. That is, when operating in the BP mode, we can see that the signal that we want to receive has passed. The operation of the filter in the BP mode corresponds to the frequency response indicated by blue in Fig. 7 (a).

When operating in the BS mode, it can be seen that there is a strong interfering signal through the parasitic resistance, and operates to remove the interference signal like the frequency response shown in FIG. 7 (b).

The main purpose of this conversion filter is to remove the interference by switching to the BS mode when there is a strong interference other than the signal to be received and by switching to the BP mode in the case of a weak interference environment, In order to prevent performance deterioration at the receiving end including the LNA stage in an environment where the spectrum state of use is continuously changed by a single filter structure which is miniaturized by passing only the LNA stage.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be apparent to those skilled in the art that various modifications may be made without departing from the scope of the present invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (10)

A common inductor and a capacitor that switch between any one of the BP mode and the BS mode to provide a coupling M _1,2 (J ₁₂ ) between the resonators in a band pass-to-band stop (BP-BS) mode,
Two switch couplers located on both sides of the common inductor and the capacitor to provide an input / output coupling Q _e (J ₀₁ )
A resonance frequency of the BP mode or the BS mode is determined by using the characteristic in the switch on / off state between the common inductor and the capacitor and between any one of the switch couplers and between the common inductor and the capacitor and the other switch coupler. And a resonator of a band pass-to-band stop (BP-BS) mode,
The resonator of the BP-BS (band pass-to-band stop) mode includes a first switch bank in which a plurality of switches are connected in parallel, a second switch in which a plurality of switches are connected in parallel, A capacitor (C1) connected in series with the first switch bank, and an inductor (L1) connected in series with the second switch bank. The variable bandpass filter according to claim 1, filter. The resonator according to claim 1, wherein the resonance frequency is changed by adjusting the number of ON and OFF states of a switch formed in the resonator of the BP-BS (band pass-to-band stop) Variable Bandpass - Bandstop Switching Filter Using Banks. 2. The method of claim 1, wherein the common inductor and capacitor
A first passive terminal having an electrical coupling value (C ₁₂ ) operating in a bandpass mode to pass a specific frequency band in an incoming signal;
A second passive terminal having a magnetic coupling value (L ₁₂ ) operating in a band-stop mode to cut off a specific frequency band in an incoming signal,
A first switch for switching a signal of an input terminal to be inputted to either the first manual input terminal or the second manual input terminal,
And a second switch for switching the output of one of the first passive terminal and the second passive terminal to be output. 2. The switch of claim 1, wherein the switch coupler
A third passive terminal having an electrical coupling value (C ₀₁ ) operating in a band pass mode to pass a specific frequency band in an input signal,
And a third switch connected in parallel with the third passive terminal to bypass an input signal bypassing the third passive terminal. delete The method according to claim 1,
In the BP-BS (band pass-to-band stop) mode resonator, when one of a plurality of switches included in the first switch bank and the second switch bank is turned on, a parasitic resistance is generated in the on- Frequency bandpass-bandstop switching filter using a switch bank. The method according to claim 6,
Wherein the resonance frequency is varied by adjusting the number of off (or on) states of a plurality of switches included in the first switch bank and the second switch bank. - Bandstop switching filter. 8. The method of claim 7,
As the number of switches turned off in the BP mode increases, the resonance frequency gradually decreases,
Wherein the resonance frequency is gradually decreased as the number of switches turned off in the BS mode increases. The method according to claim 1,
Wherein the switch is switched to the BP mode when the switches of the first switch bank and the second switch bank are both turned on, and the switch is switched to the BS mode when the switches are both off. 10. The method of claim 9,
When an interference signal other than a signal to be received has an interference that is stronger than a preset threshold value, it is switched to a BS mode, and when the interference environment is weaker than a predetermined threshold value, Frequency bandpass-bandstop switching filter using a switch bank.

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